The DNA fingerprinting and banking of tissues of the rodent strains maintained in the NIH Animal Genetic Resource (NIHAGR) has taken on a greater urgency since most of the strains are in the process of being cryopreserved. To monitor the success of inbreeding programs at the NIHAGR as well as to maintain consistent standards for investigators utilizing these strains, our laboratory processes tissues from representative offspring to ultrapure DNA. This material is then used in DNA fingerprinting with multilocus probes to confirm the results of routine genetic monitoring using isozyme analysis. In addition to the data maintained on rats and mice, we have also demonstrated that hamsters, guinea pigs and pigs bred from closed breeding groups could be differentiated by this technique. (This is a continuation of Intramural Research Project Z01-RR-10436-05 VR.)